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Tire pressure?

Old 05-22-11, 01:17 PM
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Tire pressure?

Curious as to what psi everyone is running. Tubed or tubeless. And also are you using different tire pressure depending on the type of terrain?
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Old 05-22-11, 01:22 PM
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I'm running 700cc cyclocross tyres, so I run at 75 psi

If you're curious about psi, always run at recommended psi that's listed on the sidewall and then adjust about 10 psi either above or below that level to your standards

I do deflate about 25 psi out when I'm rock scrambling, but I keep up to 75 especially for hill climbs
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Old 05-22-11, 02:27 PM
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Reason i ask is the guy at my LBS said you should never run less than 40 with tubes. On the ride i went on this morning i was running 40 but it seemed like i could of benefited from less tire pressure given the terrain(lots of rocks). Instead of my tires gripping and eating up rocks they were kind of bouncing/rolling/popping off them. Im a pretty aggressive rider so am i at risk of blowing a tube if i run less psi?
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Old 05-22-11, 05:26 PM
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you probably won't pinch flat anything lower than 30. i run 40 in the back, 35 up front.

also, i ******** love paradise, ca. my friends and i take trips up just to ride the log flumes. it's almost a tradition.
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Old 05-22-11, 05:44 PM
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Well, there's a thread on tire pressures in one of the newbie stickies. I think it's the FAQ one.

In any case, I've found ~30psi works well for me. Weight and tire size will probably play a big role in this, though. I run MotoRaptor 2.24", weight ~150lbs, and have some really rocky climbs where I ride. Otherwise I'd probably run higher psi. I know smooth single-track and lower volume tires would definitely have me ripping down some trails at a higher psi, but then I wouldn't have the grip or cushion for the rocky areas.
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Old 05-22-11, 05:50 PM
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before each ride, i look at my tires and tell them they better not let me down, i'm totally counting on them, and if they screw up i'm gonna throw them out. this seems to put the right amount of pressure on them.

(actually, they are tubeless, i think i run them about 40)
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Old 05-22-11, 05:58 PM
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Originally Posted by roastbeef
you probably won't pinch flat anything lower than 30. i run 40 in the back, 35 up front.

also, i ******** love paradise, ca. my friends and i take trips up just to ride the log flumes. it's almost a tradition.
That's awesome i actually live on the feather river canyon where one of the flume systems up here is located and ride it damn near everyday. If you are ever in the area hit me up and well go shred some trails.

Anyways im running pretty big tires i do believe a 2.35 in the rear and a 2.5 up front. Im gonna try 35 next time i go out and see if that helps. Thank you all for the input.
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Old 05-22-11, 06:22 PM
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I run 40 psi front and back with tubes...never one pinch flat. Im about to convert over to tubeless.
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Old 05-22-11, 06:58 PM
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Originally Posted by YamiRider1316
Im gonna try 35 next time i go out and see if that helps.
Optimal tire pressure is dependent upon the size and type of the tire, width of the rim, weight and riding style of the rider, and the terrain. Experimentation is the only way to decide what works best for you. And it looks like you're on the right track.
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Old 05-23-11, 03:40 AM
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I typically run 2.25 schwables (Racing Ralph and Rocket Ron) - I'm normally in the low 20s... 23PSI in the rear, 21PSI on the front; if it's loose and smooth - just a little more if it's really rocky. (I check my pressure with a digital gauge, my pump would register a little higher than these figures). With tubes I'd stick in the high 20s. One of the major tubeless advantages is you can get away with running quite low pressure. Obviously with 2.1 or narrower tyres you have to run higher pressure to get a similar ride.
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Old 05-23-11, 08:08 AM
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Currnetly running tubeless ignitor 29ers, fully rigid. 18 front, 20 rear. Not even kidding. Trail chatter is definitely not a problem.
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Old 05-23-11, 08:43 AM
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Originally Posted by frankenmike
Currnetly running tubeless ignitor 29ers, fully rigid. 18 front, 20 rear. Not even kidding. Trail chatter is definitely not a problem.
You must weigh something like 90lbs. Because if my 210lbs fat ass got on anything with 18psi tire pressure I'd be riding on the rims.
I run around 32psi give or take a couple of pounds depending on the terrain.
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Old 05-23-11, 11:39 AM
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Originally Posted by cryptid01
Experimentation is the only way to decide what works best for you.
I’m surprised we still get this question, since the guesswork was taken out of this a long time ago. A simple mathematical formula can determine the right psi to run in your tires for the given situation:



uv = the total volume of air in your particular tire/tube (or tire, in the case of tubeless) by the Beta (β) factor of the center depth of your rim.

p1 = initial tire pressure, factored by the psi load-bearing capacity-without-deflection (CWD, expressed in N) of the particular soil/substrate you ride on most and the surface’s ambient rolling resistance (noise).

p2 = Max tire pressure for the given conditions, factored by your weight, the bike’s weight, mean barometric pressure for the season and the radius (r) of your rim's ERD.

p3 = OPTIMAL tire pressure given all the above factors, factored by the cosine of your average velocity and taking into account the c1 - - or the averaged amplitude and wavelength of pointed and square-edged features encountered on the typical trail you ride (the last factoring formula).

It’s easy - - just plug in your numbers and you have your tire pressure.
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Old 05-23-11, 11:49 AM
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I'm sorry. Doug can you repeat that again please? I think you forgot to add in the FS (fat ass) factor to that formula.
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Old 05-23-11, 11:51 AM
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I did something wrong on the equation. I plugged in my numbers and got that the end of the world is June 15. Doug, what did I do wrong?
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Old 05-23-11, 12:05 PM
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^^ Many people make that error by forgetting that you need to use the cosine of your average velocity, rather than the arctan. The arctan, or actually its inverse, was erroneously included in early unpublished models of the formula (probably what you were thinking of and just automatically plugged in the number). This unfortunate error led to the 2003 event in which a team of bicycle engineers sold their belongings, drove to Area 54 and died in the desert waiting . . . and waiting . . . .
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Old 05-23-11, 12:49 PM
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Originally Posted by mystolenbikes
You must weigh something like 90lbs. Because if my 210lbs fat ass got on anything with 18psi tire pressure I'd be riding on the rims.
I run around 32psi give or take a couple of pounds depending on the terrain.
I would've thought the same thing, but my 225 lb. weight seems fine with that pressure. I actually started at 30, decreasing incrementally on succesive rides before arriving at my current preference in the 20 range.
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Old 05-23-11, 01:03 PM
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Area 54, oh is that the one by Dogbone Lake? I made the corrections and yes, 35 rear and 40 front. That's better.
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Old 05-24-11, 03:58 AM
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Been riding 25 up front, 30 in the rear for a while. Starting to get much more aggressive on the trail and suffered a pinch flat or two. Going up to probably 28 and 33 or something. About 185-190lb with a hardtail on rocky terrain.
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Old 05-24-11, 12:19 PM
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Originally Posted by pablosnazzy
before each ride, i look at my tires and tell them they better not let me down, i'm totally counting on them, and if they screw up i'm gonna throw them out. this seems to put the right amount of pressure on them.

(actually, they are tubeless, i think i run them about 40)
You gotta admit, that is some good bike humor!
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